


Little

by Sonamyluffer101



Series: Commissions [2]
Category: Undertale (Video Game)
Genre: Alternate Universe - Horrortale (Undertale), Animal Instincts, Animalistic, Animalistic Sans (Undertale), Big monsters, Come Inflation, Cunnilingus, Dark Past, Ecto-Penis (Undertale), Ecto-Tongue (Undertale), F/M, First Time, Horrortale Sans (Undertale), Oral Sex, Rough Sex, Size Kink, Smut, Stretching kink, Territorial Sans
Language: English
Status: Completed
Published: 2019-06-19
Updated: 2019-06-19
Packaged: 2020-05-14 22:35:42
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,403
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/19282576
Author URL: https://archiveofourown.org/users/Sonamyluffer101/pseuds/Sonamyluffer101
Summary: You've been together for a while, and yet you've never slept together... you would assume monsters just didn't have sex like humans did, but...That definitelywasn'tthe case.





	Little

**Author's Note:**

  * For [Landy_Ano](https://archiveofourown.org/users/Landy_Ano/gifts).



> This is a commission for [Landy_Ano!](https://archiveofourown.org/users/Landy_Ano/pseuds/Landy_Ano) I hope you enjoy it!
> 
> I take commissions through my discord server, which is down below in the end notes <3

Eight months of dating seemed like a lot to go without having any sexual contact.

 

The most you had ever done with your boyfriend was kiss and hug… you hadn’t even slept in the same  _ bed _ before, let alone cuddled in any sense of the word. You had assumed for a while that he might have been asexual, or that monsters were in general, but you talked to him about it, and well… that definitely wasn’t the case. He had just been scared of hurting you, and you couldn’t fault him for that. He cared about you, and he was just trying to make you happy and comfortable.

 

But, after eight months, you finally convinced him to come over to your place. You knew it took him a while to grow used to people, to be comfortable around them, but… it seemed a little too long to you, so you finally asked.

 

You were so happy when he agreed… but… you were also a nervous mess.

 

You planned to ask him about sex, but you weren’t quite sure  _ how _ to ask him, and you didn’t have time to try and figure it out, either. You spent the entire day cleaning up around your apartment and trying to make sure it was  _ perfect _ for him. You didn’t want to look like a slob, especially not when his house was pretty spotless, thanks to his brother. Papyrus was… definitely a neat freak, somehow, even after everything that monsters had been through underground. Starvation, cannibalism… they suffered through so much, and you felt like they deserved the world after that.

 

So really, the least you could do was have a clean apartment for him, and a nice meal.

 

You made sure to make something you knew would be filling and delicious, so you went with beef stew. You needed to make sure he was happy and full before asking, so you had the best chance.

 

...You really hoped he would say yes. You had never been the type who craved sex, but… you really,  _ really fucking wanted him. _

 

You had been organizing your bookshelf when you heard a knock on the door… you were a little disappointed you couldn’t finish, but you knew it was just a small detail you were knit picking at this point. Plus… that meant he was here, and you had so many butterflies in your belly knowing that… it had taken so long to get to this point.   
  


You practically ran to the door before pausing in front of it momentarily, and then you pulled it open after taking a deep breath.

 

As expected, there he was. Sans was stood outside the door on your front step, peering down at you. He was so tall that he could barely see you past the top of the door frame… it made you smile.

 

“Hi!” You greeted him, happily. 

 

“...hey,” His voice was deep, and he hesitated momentarily as he peered past you into your apartment for a second, before looking back to you.

 

You made sure to smile reassuringly. “Come on in! Food’s almost ready.”

 

You watched as he ducked his head under the door frame. You knew that might be an issue, and you were worried he might hurt his head, or God forbid hit his crack on the door frame, so you got some foam padding and stuck it onto the frame to prevent the pain.

 

He stood inside and looked at the frame, noticing the padding now that he was inside. You were about to say something. But he started to poke at it.

 

“...hm.” He seemed curious… he probably didn’t even know what it was.

 

“...It’s foam. It will keep you from hurting your head,” You explained, chuckling a bit as he stopped squishing it.

 

“soft... smells like cleaner in here.”

 

“...I cleaned the apartment.”

 

He seemed so… disappointed, somehow. You weren’t quite sure why.

 

You went back to the kitchen and finished up the stew, before spooning it into two bowls… you made sure his portion was a lot larger than your own, since he was able to eat so much more than you. A small soup bowl for you, and an entire mixing bowl for him.

 

“Here we go!” You said, before setting the bowls down on the table. He took a seat in one of the chairs, and… it was almost comical how big he looked. He could barely fit in the seat, but neither of you said anything.

 

You both began to eat in silence… you weren’t sure what to say, and clearly neither did he.

 

His stew was gone in less than a minute, and you hadn’t even eaten two spoonfuls yet, so you felt a little awkward as he just watched you eat… but after a moment, he broke the silence, thank God.

 

“...why did you ask me to come over?”

 

You blinked. You didn’t exactly… have a good answer for that. Usually you would go to his house, so of course this seemed  _ off _ to him. You couldn’t just out right say ‘I want to fuck you’. That just… you  _ couldn’t. _

 

“...Just wanted to spend some time together. Just the two of us.”

 

He raised a brow bone as he stared you down. You felt so small… you could tell he could see right through you. If you just wanted to spend time together you could go to his house and hide in his room like you usually did… but, you were afraid Papyrus might hear you if Sans agreed to sleeping with you.

 

You could feel your cheeks heating up, turning bright red as you thought about it. You were going to have to tell him now, and that was  _ so _ scary to you.

 

“...Wanted to…  _ ‘Netflix and chill’. _ But… only if you want to…” You hoped he would understand that, but you really had no idea if he knew what that meant.

 

He blinked. “...netflix and chill?”

 

_ “Sex.” _

 

…

 

...You regretted saying it as soon as it came out of your mouth.

 

“oh.”

 

…

 

That was all that he said, and you felt very strange about it, so all you could do was just… eat. That wasn’t a proper answer, so how in the hell were you supposed to respond?... You couldn’t.

 

“okay.”

 

…”...Okay?”

 

“mhm. but if i start scaring you… tell me,” He said, sounding stern, but… you didn’t care. You knew he couldn’t scare you, you were excited as hell!

 

“Alright!”

 

“finish eating first,” He told you, before standing up and going up the stairs. You knew he was going to your room… you would meet him up there after you ate.

 

But that didn’t mean you didn’t eat as fast as you could. Thankfully the food wasn’t so hot that it burnt your tongue or the roof of your mouth.

 

You were afraid of giving yourself indigestion, but… that didn’t stop you. You still shoved it in your mouth and didn’t even bother rinsing out your bowl after you were done. You just put it in the sink and went up to your bedroom.

 

You were a little surprised to see that he had already taken his shirt off… but you weren’t about to complain. Despite the fact that he was sat on your bed, you were more than positive that he had gone through your stuff, especially since one of your socks was peeking out of your underwear drawer now.

 

You walked over to him, and you were pleasantly surprised when he pulled you into his lap… he had always been the distant type. If you wanted a kiss, you went to him, if you wanted a hug, you went to him. You knew he didn’t mean anything bad by it, and that he loved you, but… sometimes it sucked. He was very broken, and you saw that in his actions as well as his words. Sometimes he would say the wrong thing, but that wasn’t his fault. Trauma affected him.

 

He began to remove your shirt from your body… something that you weren’t expecting. You let out a shaky breath as it was pulled over your head, feeling exposed now that you were sat in his lap, in your bra. He was taking initiative… you were so happy and excited. You hoped it would stay this way, and that his confidence would be permanent. You loved him so much, and you knew he could be so strong, especially after everything he had been through… he didn’t have to bend and break from his past. He could learn from it and grow.

 

Your stomach felt cold now, exposed to the air, but he placed one hand on it and you felt  _ good. _ Even confident. You touched his rib cage, and you were happy when he didn’t make you stop. He had done it before.

 

“...i don’t know how this is going to feel for you,” He told you, rubbing your belly. You hummed, knowing you would feel perfectly fine.

 

You kissed him on his jaw to show you were okay… you wanted this.

 

“i know the size difference is gonna be hard,” He said, stumbling slightly over his words… you knew he wasn’t very good at this type of thing, or speaking in general. It took him forever to speak to you in the first place.

 

You smiled at him. “It’s okay. We’ll just take it slow.”

 

You knew you would be okay.

 

His voice got quiet when he spoke again. “...i don’t want to hurt you.”

 

You felt butterflies go off in your belly.

 

“It’s alright. I’ll tell you if it’s hurting.”

 

“i think it’s inevitable.”

 

...You had to admit, that was a little nerve wracking. Regardless, you kissed him, and tried not to show any fear whatsoever. It was pretty easy, since you enjoyed kissing him anyways.

 

You felt his hand move up to grab your breast, but… he didn’t. Instead, he tore your bra off, literally ripping it in half. You let out a small gasp, surprised and very turned on… he was just… so  _ big _ and strong. It was terrifying and arousing, and you were just… so fucking horny. You were going to miss that bra, yes, but it felt worth it.

 

You lifted your butt up so he could take your pants off, and he brought your underwear with it. You felt… so fucking weak being naked in front of him. He could crush you with his bare hands, and instead he wanted to sexually please you. That was so arousing.

 

You felt him stand and lift you like you were weightless, before laying you down on your bed properly. You got comfortable as you watched him take his pants off, but leave his boxers on… they were dark blue. You liked them.

 

You were a little surprised when he went and settled himself between your legs… you weren’t a virgin, but… you had never been eaten out before. You were excited, but also a little scared. What if he… didn’t like it or something? What if you didn’t?

 

You felt his tongue run up your entire pussy, stopping at your clit to focus on that… Jesus, his tongue was  _ huge. _ It covered every inch of your cunt, and it was incredible… you were in  _ awe. _ You couldn’t stop moaning the second it touched you. You gripped onto your bedsheets, taking deep breaths. You couldn’t believe how this felt… it was  _ so _ fucking good. So intense and  _ fast. _ You could already feel your stomach tightening, ready for orgasm, but it wasn’t quite there yet.

 

He tongue circled your bundle of nerves, and you could barely breathe, let alone think. You were just chasing that sweet release, desperate and hungry for it.

 

You reached down and clung to his shoulders, afraid to touch his skull and accidentally hit the crack. You just wanted to cum, and you were already overwhelmed as fuck. Your body had never been so intensely pleasured.

 

But finally, something snapped in you like a rubber band, and his tongue became too much.

 

Your body pulsed and contracted, and you had to pull away from him, closing your legs and catching your breath. You couldn’t handle anymore… there was no way.

 

He sat up and rubbed your belly as you caught your breath, but you couldn’t help but notice the way he stared at your tits like a hungry animal… it turned you on again, _ already. _ Your clit was throbbing again, and you were amazed that your body could handle that.

 

He brought his eye light up to look at you, and you wanted to moan from his gaze alone.

 

“...wanna go further?” His voice sent shivers down your spine.

 

“Y-Yes!” Even you were a little surprised by how desperate you sounded.

 

You felt him reach down between your legs and slowly push one of his fingers inside of you. You gasped, caught off guard a bit… it was so  _ big? _ You were shocked by how much of a stretch you already felt… it made your confidence waver a bit. Were you going to be okay through all of this?

 

You whined softly, and he kissed you on the cheek. 

 

“shh.”

 

“S-Sans,” You moaned his name gently, holding onto his shoulders again for support.

 

“shh,” He repeated, adding another finger in, making you bite your lip… it was almost too much. It almost hurt… but not quite yet.

 

“does it hurt?” He asked after a moment, wiggling his fingers a bit.

 

You shook your head in response, afraid of your voice cracking if you spoke. You just needed to wait it out. The pressure wasn’t forever… you could already feel yourself growing used to it, anyways.

 

“...alright.”

 

He added a third finger, and you had to stop him.

 

“T-Too much,” You said, quickly, your voice breathy, and cracking like you knew it would.

 

He stopped moving right away, and you were glad he didn’t pull his fingers out. You would be fine, you just… needed some time to adjust, is all. You could do this… you were confident in yourself.

 

He kissed your forehead and you smiled. He was so sweet when he wanted to be.

 

“you’re okay. deep breaths.”

 

You took a few, and decided you would be okay… you had just been nervous, after all.

 

“...O-Okay. I’m okay. I’m good.”

 

He wiggled his fingers, and you gasped… it… felt better. It didn’t hurt or feel too much like stretching anymore. Jesus, you adapted faster than you thought you would.

 

“good?”

 

You nodded again, and you felt his thumb begin to circle your clit… it was still sensitive, and it made you twitch a little, and whine softly. 

 

“...good girl,” He praised you, making your face heat up even  _ more _ somehow.

 

“S-Sans, please!”

 

He made a small humming sound, to signal he was listening and wanted you to continue.

 

“P-Please fuck me!” You were desperate at this point… you didn’t want to wait anymore. No more build up, just… you wanted the real thing, and you wanted it  _ now. _ You heard him laugh, his voice deep, making you want him even more… you felt him pull his fingers out very gently, and you just felt empty. 

 

You watched as he pulled his dick out of his boxers, not bothering to take them off, and then hovered above you. You were… shocked by the size. You knew he was going to be big, but… that was just  _ huge. _

 

He began to push in, and you had to cling to his arms. You were able to fit him in beacuse of all of the stretching, but  _ fuck _ it was still so much… even at the snails pace he was going, you felt so sore. You knew the next day you were barely going to be able to function, let alone walk.

 

“...W-Wait,” You said, once he reached about half way in. you had been biting your lip, and you could tell you were about to draw blood. 

 

“...hm?” He sounded sort of strained, and it made you feel a little bad. He was holding back  _ so much, _ and you could visibly see that on his face and hear it in his voice.

 

“...Just… need a second,” You admitted, looking down to see how big he looked between your legs… you couldn’t believe you were only half way there.

 

You took deep breaths, and while you did so, he played with your breasts. You were glad he had something to occupy himself with, especially since you knew it must be hell for him to wait while he’s actively inside of you. You knew instincts were a thing, and his were probably a mess because of you.

 

After a few moments, you spoke up. “...Okay… y-you can move again.”

 

You certainly didn’t have to tell him twice.

 

He began to push inside once again, a little faster than before. You were okay… it didn’t hurt, thankfully. You were able to handle the stretch, and eventually, he managed to bottom out inside of you.

 

You had never felt so  _ big _ in your entire life. You were surprised he was even able to  _ fit _ all the way in.

 

You looked up at him, about to comment on it, but… you stopped short. He looked… completely out of it. His one eye light had extinguished, and he didn’t even look like he was in there. It was almost like an  _ actual _ skeleton was above you, and it made you uneasy for a moment.

 

You didn’t know what to do, so you just… touched his rib cage, hoping it might ground him.

 

“...hands off,” He said, his voice pretty deep and stern. It made you stop right away.

 

You were confused, and honestly a little spooked, but… you didn’t wanna question it.

 

After a few moments, his eye light returned, and you were glad he looked like him again.

 

“...okay. i’m okay.”

 

“...You’re alright,” You agreed, reassuring him.

 

He began to move, just a little bit, slowly pulling out the smallest bit and then pushing back in, more and more as time went on. You were quiet, trying to adjust and get used to how it felt… it was easier than you ever expected. You hadn’t experimented much with stretching in the past, since it always seemed so scary, but this was… easier than you ever would have expected.

 

“...are you okay?” He asked after a bit, at the point where he was able to pull out half way and push back in easily enough.

 

“...Mhm,” You assured him, clinging to him, your arms wrapped around his neck. He clutched at the bed frame as he thrusted into you, your entire body moving with him. 

 

You could feel him slowly getting rougher, and the one hand that was gripping onto your hip was starting to bruise… you could just feel it. He was growling above you, something you weren’t sure if you had  _ ever _ heard before then… it scared you a little, but it was also somehow arousing.

 

He bit your shoulder suddenly, and you screamed a bit… it hurt, but it wasn’t unbearable. You could just tell he was starting to lose himself, and that was a little terrifying. He warned you about this, and you still wanted it.

 

“S-Sans,” You moaned out, as he began to thrust harder and faster. You were close to another orgasm, and him licking your shoulder somehow pushed you over the edge. You came, and in turn, your pussy contracting around him in such a way pushed him over the edge as well, making him cum inside of you.

 

...There was  _ so _ much of it.

 

He let go of the headboard, and you could just hear how bad it was splintered without even looking up at it. He let go of your hip, and it was  _ so, so _ sore… looking down you could see that your stomach inflated slightly… just a little bit. Sans himself looked like a mess, his face dusted dark blue as he rubbed your stomach softly before pulling out.

 

You shivered, sensitive and empty as you felt cum drip down your thighs.

 

He laid down beside you and held your hand… you felt  _ good  _ despite how sore you were.

 

“...I don’t think I’ll be able to walk tomorrow.” Your voice was hoarse and sore from all of the screams and moans you made… it hurt to talk. You really needed some water.

 

“i’ll carry you.”

 

“Please.”

**Author's Note:**

> [My Tumblr.](https://www.tumblr.com/blog/skelesansation)
> 
>  
> 
>  
> 
>  
> 
>    
> [My Twitter.](https://twitter.com/skelesansation1)
> 
>  
> 
>  
> 
> [Discord server! Come chat. 18+.](https://discord.gg/f4xn8rB)


End file.
